A) Field of the Invention
The present invention relates to a light emitting device such as an LED array and automotive lightings including an LED array.
B) Description of the Related Art
There are demands for large output LED elements designed for use in automotive headlamps and lightings. Simply increasing the areal size will necessitate a large driving current, which is difficult to flown uniformly in a semiconductor chip. A known solution is to divide the LED device into a plurality of LED elements and connect the plurality of LED elements in series (see, for example, patent documents 1, 2, and 3).
Applications such as automotive headlamps require a horizontally extended flux of light. This is achieved by a plurality of LED elements arranged or aligned horizontally. If LED elements are prepared separately and arranged along a horizontal line on a support substrate, an interval of 100 μm or more is practically required between adjacent pair of LED elements.
FIG. 6A is a schematic plan view of a conventional LED array 200, and FIG. 6B is a partial cross section of the LED array 200 depicted in FIG. 6A along virtual line cd. Four nitride semiconductor light emitting diode elements (LED elements) 201 are disposed and connected in series on a support substrate, such as a Si substrate 230 provided with an insulation film 207. As illustrated in FIG. 6B, each LED element 201 contains a light emitting structure 202 made of lamination of an n-type GaN layer 221, an active layer 222, and a p-type GaN layer 223 stacked in this order from the top; a p-side electrode 212 formed in contact with the p-type GaN layer 223 on a rear surface of the light emitting structure 202; an n-side electrode 208 of parallel stripe shape in contact with the n-type GaN layer 221 on top of the light emitting structure 202; an insulation film 210 covering from the top surface to the side surface of the light emitting structure 202; and interconnection wiring 211 elongated from the n-side electrodes 208 and extending from on the insulation film 210 to on the p-side electrode 212 and connected to the p-side electrode 212 of the adjacent LED element (for the rightmost LED element, no LED element exists on the right-hand side and the wire 211 serves as a lead wire).
Patent document 1: Japanese Unexamined Patent Publication (Kokai) No. 2008-034530.
Patent document 2: Japanese Unexamined Patent Publication (Kokai) No. 2009-206246.
Patent document 3: Japanese Unexamined Patent Publication (Kokai) No. 2010-015887.
As illustrated in FIGS. 6A and 6B, intervals of about 100 μm or more are practically required between adjacent LED elements if separate LED elements are assembled on a support substrate. If a lighting apparatus is produced by utilizing a phosphor or fluorescence powder-containing sealing resin layer covering a plurality of LED elements, the resulting emitted light will be nonuniform in brightness distribution and chromaticity distribution. It will be difficult to achieve uniform brightness and uniform chromaticity distributions.